If you are vanity publishing and just want to see your stuff on the web, it is very, VERY easy to get involved with. Of course, your writing is not likely to stand out if you don't have a clear plan. The more I use it, the more I like it. The user interface is extremely well-done. I kinda wish my WordPress-based blogs had editors that were that easy to use.
It can be harder to get your content seen as medium is a popular platform.
It is still early days for us to track back success (traffic, rank etc) from posting to medium regularly. I hear tracking success outside vanity metrics can be hard for others too.
I am yet to figure out how to create and add to magazines - these have the potential to be a good audience booster, but not too clear.
We found the support desk of Medium to be really good. They are very focussed on customer service and are willing to go all out to help in every way they can. They are fast to respond and they are also very knowledgable at what they do. They know the importance of being customer-focused.
Medium is easy to use. It is easy to add highlights and emphasis in paragraphs. It is easy to add images and videos anywhere in your articles. It makes article writing fun and easy to share. Other products were more cumbersome and awkward to use or were more expensive to operate.